This invention relates generally to systems for heating water by means of solar radiation and in particular to water heating systems utilizing auxiliary heaters and a system circulation pump.
Devices for heating water from the sun's rays are well known in the art. However, a problem which must be addressed in any such heating system is how to maintain a supply of hot water either when the sun isn't shining, e.g. during the night, or particularly during prolonged periods of cloudiness, or when the demand for hot water exceeds the solar heating system's ability to provide it.
The most common solution to this problem is to have a conventional heating source available as an auxiliary back-up in times of need. Typically, this auxiliary heating requirement employs a heating loop connected to a heat exchanger inside a hot water tank or reservoir and to a thermostatically controlled external heating source. Alternatively a thermostatically controlled electric immersion heater can be employed by inserting the heating elements directly into the tank. The thermostat typically senses the temperature of the water in the tank, and, if the temperature falls below a predetermined value, activates the auxiliary heater.
These systems perform satisfactorily, however, they require installation of a heat exchanger in the solar heating fluid flow circuit as well as the installation of, for example, an electric immersion heater. The associated reservoir is therefore different than a conventional tank and the cost of the reservoir is thus increased.
In a solar heater built in accordance with the present invention these drawbacks are avoided. It is thus an object of the invention to provide an auxiliary heating unit for a solar hot water heater which is completely external to the hot water reservoir and which will rapidly heat water and supply it into the reservoir when needed. Another object of the invention is a solar hot water heater having an auxiliary heater which can be adapted readily to an existing conventional hot water tank with at most minor modifications of a standard tank. Other objects of the invention are a simple, reliable solar hot water heating system requiring minimum installation cost and efficient operation.